Apparatus, medium, and method for photographing based on face detection

ABSTRACT

A photographing method, medium, and apparatus based on face detection in a portable camera. The portable photographing apparatus may include an image input unit that receives an image, a face detection unit that detects a face from the received image, a storage unit that stores the image detected by the face detection unit as a moving image in a first mode, and a quality evaluation unit that evaluates the quality of the image detected by the face detection unit and stores the same as a still image in a second mode upon satisfaction of predetermined conditions evaluated based on the quality evaluation of the still image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority benefit from Korean Patent ApplicationNo. 10-2004-0113805 filed on Dec. 28, 2004 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a photographingapparatus, medium, and method, and more particularly, to a photographingapparatus, medium, and method detecting a still image and/or movingimage of a to-be-photographed person based on face detection andexamining the quality of the detected image, thereby providing ahigh-quality still and/or moving image of the to-be-photographed person.

2. Description of the Related Art

Recently, along with the advancement of semiconductor and imageprocessing technologies, portable digital cameras, camcorders, cellularphone cameras, and the like, that include built-in mobile communicationdevices with digital camera capabilities, which will be called ‘portablephotographing apparatuses’ hereinafter, have emerged and gainedpopularity. The portable photographing apparatuses are capable ofphotographing not only still images but also moving images of ato-be-photographed person. In particular, the portable photographingapparatus has widely been used in photographing the to-be-photographedperson.

Despite widespread use, it has been found that the portablephotographing apparatuses have several problems. When a still image of aperson is to be generated, it is quite difficult to determine the properlocation of the to-be-photographed person. For instance, a photographermay want to photograph the face of a person who is continuously moving.In such a condition, it is not easy to spontaneously take a picture byaccurately pressing the shutter at the moment when the face of theperson is accurately positioned at a proper location.

In this connection, Korean Patent Published Application No. 2004-0017998has discussed the increasing of accuracy of a captured image byoutputting a guide message for directing an orientation of the person tobe photographed to be positioned at the center of an image sensor for anaccurate face image, i.e., by providing the to-be-photographed personwith time for correcting the position of his/her face. In addition, U.S.Pat. No. 6,636,694 has discussed the providing of a guide as to properorientation of a to-be-photographed person for positioning of the pupilsof a to-be-photographed person when photographing a photo for anidentification card or a passport.

However, here, these discussions relate to of the directed orientationof the face of a to-be-photographed person at a predetermined positionusing a fixed camera, and is not suitable for applications of portablephotographing apparatuses, e.g., for attaining a high quality faceimage.

In addition, even when a portable photographing apparatus is used inphotographing a moving image, the available photographing time mayusually be shortened due to the limited memory capacity of the portablephotographing apparatus. For instance, unnecessary background images maybe stored even though only a moving image of a to-be-photographed personis desired, resulting in the wasting of memory space.

Here, Japanese Patent Published Application No. 2002-176619 discussesthe clipping and transmitting of only frames, among pre-recorded movingimage frames, where a to-be-photographed person faces the front of aportable communication terminal, with frames having sound exceeding apredetermined level being determined as corresponding to the faceoriented frames. According to this discussion, however, since imagesequences of a face are clipped from previously photographed movingimages, using the portable communication terminal, it is quite difficultto store moving images of the user using a portable photographingapparatus on a real-time basis.

Meanwhile, to photograph a to-be-photographed person, using the portablephotographing apparatus, the to-be-photographed person should bepositioned at the center of a focusing area. In conventionalphotographing apparatuses having distance-based auto-focusingcapabilities, focus is adjusted in the center of the image withoutregard to the position of the to-be-photographed person. That is to say,no direct solution for auto-focusing has yet been proposed.

Thus, it has been found that in order to take a still image of a personto be photographed, using a portable photographing apparatus, it isdesirable to automatically identify the position of the face of theto-be-photographed person to notify a user of the portable photographingapparatus of an appropriate photographing state. In addition, in thecase where the user intends to take a moving image of theto-be-photographed person, moving images of the to-be-photographedperson should be stored only when a face of the of theto-be-photographed person is detected, thereby extending the availabletime for which all moving images can be stored, i.e., additional movingimage data can be stored.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a portable photographingapparatus, medium, and method photographing a high quality still imageand/or moving image of a to-be-photographed person, e.g., using aportable photographing apparatus having a face detection capability.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth a portable photographing apparatus,including a face detection unit to detect a face from a received image,a storage unit to store the received image upon detection of the face asa moving image in a first mode, and a quality evaluation unit toevaluate a quality of the received image and to store the received imageas a still image in a second mode upon a satisfaction of a selectivepredetermined condition evaluated based on a quality evaluation of thereceived image.

The portable apparatus may further include an image input unit toreceive the image as the received still image. In addition, the facedetection unit may include a subwindow generation module to receive animage from the image input unit and generate a subwindow correspondingto the received image, a first face search module to receive thesubwindow from the subwindow generation module and to detect a face fromthe subwindow to determine whether a frontal-view face exists, a secondface search module to, if the frontal-view face is detected by the firstface search module, sequentially detect two mode faces among a firstmode face generated by up and down facial rotation, a second mode facemade by a leaning of a head to either side of left and right sides, anda third mode face made by left and right facial rotation, and a thirdface search module to detect a remaining mode face not detected by thesecond face search module.

The face detection unit may further include a face detection controlmodule to generate a new subwindow to be supplied to the first facesearch module if no face is detected by any of the first face searchmodule, the second face search module, or the third face search module.

Further, the third face search module may sequentially perform anoperation of arranging face detectors for all directions in parallel,and when succeeding in face detection in one direction perform facedetection in a same direction using a more complex face detector, andwhen failing in face detection in one direction perform face detectionin a different direction, and an operation of independently andseparately arranging the face detectors for all directions, such thatwhen succeeding in face detection in one direction performing facedetection in a same direction using a more complex face detector, andwhen failing in face detection determining that a face is not detectedfrom the input image.

The second face search module may perform sequential detection of thetwo mode faces using a coarse-to-fine search algorithm. In addition, thesecond face search module may attempt detection of one of the two modefaces using a simple-to-complex search algorithm.

The quality evaluation unit may evaluate an illumination condition ofthe received image, evaluates a face size of the received image,evaluate an image blur state of the received image, and/or cause afocusing to be adjusted on the face in the received image as detected bythe face detection unit.

The apparatus may further include a user interface unit to provide for auser interface to allow a user to select a moving image mode or a stillimage mode, to provide for a user interface to allow a user to select anautomatic photographing mode or a manual photographing mode for when theface is detected, and/or to provide for a user interface to allow a userto select an image quality characteristic to be implemented for thequality evaluation.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth a method of photographing a picture in aportable photographing apparatus based on face detection, the methodincluding receiving an image, detecting a face from the received image,and storing the received image detected by the face detection unit as amoving image in a first mode, and evaluating the quality of the receivedimage detected by the face detection unit and storing the received imageas a still image in a second mode upon satisfaction of a selectivepredetermined condition evaluated based on a quality evaluation of thereceived image.

The detecting of the face may include sequentially detecting two modefaces among a first mode face generated by up and down facial rotation,a second mode face generated by a leaning of a head to either side ofleft and right sides, and a third mode face made by left and rightfacial rotation, detecting a remaining mode face that is not detected inthe sequentially detecting of the two faces, and if the remaining modeface is detected in the detecting of the remaining mode face, determinewhether the face is detected from the image, wherein the detecting ofthe remaining mode face includes arranging face detectors for alldirections in parallel to perform face detection, and independently andseparately arranging the face detectors for all directions to performface detection.

In the parallel arranging of the face detectors, when succeeding in facedetection in one direction face detection may be performed in a samedirection using a more complex face detector, and when failing in facedetection in one direction face detection may be performed in adifferent direction.

In the independently and separately arranging of the face detectors,when succeeding in face detection in one direction face detection may beperformed in a same direction using a more complex face detector, andwhen failing in face detection non-detection of a face may be determinedfor the received image.

The sequentially detecting of the two mode faces may includesequentially detecting the two mode faces using a coarse-to-fine searchalgorithm. The sequentially detecting of the two mode faces may includesequentially detecting one of the two mode faces using asimple-to-complex search algorithm.

In addition, the selective predetermined condition may be anillumination condition of the received image, a face size of thereceived image, an image blur state of the received image, and/or afocusing adjustment performed on the face in the received image.

The method may further include providing a user interface to allow auser to select a moving image mode or a still image mode, providing auser interface to allow a user to select an automatic photographing modeor a manual photographing mode for the face detection, and/or providinga user interface to allow a user to select an image quality conditionfor the predetermined condition.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth an imaging apparatus, including a facedetection unit to detect a face from a received image through amultilayer face detection scheme, with a broader face detection beingfirst applied and a narrower face detection secondly being applied,wherein the narrower face detection is only implemented after detectionof a face through the broader face detection, and a storage unit tostore the received image, upon a detection of the face, as a movingimage or a still image.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth an imaging apparatus, including a facedetection unit to detect a face from a received image through amultilayer face detection scheme, with the different layers of facedetection separately detecting for a face through respective particularaxis of movement of a face, and a storage unit to store the receivedimage, upon a detection of the face, as a moving image or a still image.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth an imaging apparatus, including a facedetection unit to detect a face from a received image through amultilayer face detection scheme, with the different layers of facedetection separately detecting for a particular potential orientation ofa face in the received image and with the different layers of facedetection being implemented with a number of face orientation detectorsless than a number of particular potential face orientations in thereceived image, and a storage unit to store the received image, upon adetection of the face, as a moving image or a still image.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth a portable photographing apparatus,including a means for face detection of a face from a received image,and a storage unit to store the received image based upon detection ofthe face as a moving image or a still image.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth a portable photographing apparatus,including a face detection unit to detect a face from a received image,a storage unit to store the received image based upon detection of theface as a moving image or a still image, and a means for qualityevaluation of the received image and to store the received image as astill image upon a satisfaction of a selective predetermined conditionevaluated based on a quality evaluation of the received image.

To achieve the above and/or other aspects and advantages, embodiments ofthe present invention set forth at least one medium including computerreadable code to implement method embodiments of the present invention.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be apparentfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 illustrates a method of photographing a picture, according to anembodiment of the present invention;

FIG. 2 illustrates a portable photographing apparatus, according to anembodiment of the present invention;

FIG. 3 illustrates directions in which a face may be rotated using athree-dimensional coordinate axis;

FIG. 4 illustrates angles at which a face may be rotated around anX-axis;

FIG. 5 illustrates angles at which a face may be rotated around aY-axis;

FIGS. 6A and 6B illustrate angles at which a face may be rotated arounda Z-axis, and alternate angles at which a face may be rotated around theZ-axis, respectively;

FIG. 7 illustrates a reducing of the number of face detectors desiredfor learning in a first Z-rotation mode for a frontal-view face,according to an embodiment of the present invention;

FIG. 8 illustrates a reducing of the number of face detectors desiredfor learning in the first Z-rotation mode for a left-view face,according to an embodiment of the present invention;

FIG. 9 illustrates faces to be learned, with respect to a frontal-viewface, in the first Z-rotation mode, according to an embodiment of thepresent invention;

FIG. 10 illustrates a reducing of the number of face detectors desiredfor learning in a second Z-rotation mode for a frontal-view face,according to an embodiment of the present invention;

FIG. 11 illustrates a reducing of the number of face detectors desiredfor learning in the second Z-rotation mode for a left-view face,according to an embodiment of the present invention;

FIG. 12 illustrates faces to be learned, with respect to a frontal-viewface, in the second Z-rotation mode, according to an embodiment of thepresent invention;

FIG. 13 illustrates a face detection unit, according to an embodiment ofthe present invention;

FIGS. 14A through 14C illustrate face search methods, according toembodiments of the present invention;

FIG. 15 illustrates the detecting of a face by combining three facesearch methods, according to an embodiment of the present invention;

FIGS. 16A and 16B illustrate the detecting of a face, according to anembodiment of the present invention;

FIG. 17 illustrates another method, according to the embodiments ofFIGS. 16A and 16B, according to an embodiment of the present invention;

FIG. 18 illustrates a still face image photographing process, accordingto an embodiment of the present invention;

FIG. 19 illustrates a motion face image photographing process, accordingto an embodiment of the present invention;

FIG. 20 illustrates a picture image view showing examples of thedetecting of face sizes, according to an embodiment of the presentinvention;

FIG. 21 illustrates a detecting for blurs, according to an embodiment ofthe present invention; and

FIG. 22 illustrates a picture image view showing an example a detectingof blurs, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. Embodiments are described below to explain the presentinvention by referring to the figures.

FIG. 1 illustrates a photographing process, according to an embodimentof the present invention.

In order for a user to photograph a still and/or moving image of ato-be-photographed person using a portable photographing apparatus,according to an embodiment of the present invention, a face may bedetected from an input image, in operation S120. The detecting of theface will be described in more detail below with reference to FIGS. 3through 17.

When a face is detected, in operation S120, an image quality of thedetected face may be evaluated, in operation S140. Here, determinationof the image quality may preferably be based on a still image of theto-be-photographed person, for example. In addition, determination maybe made as to an illumination intensity, face size, blur presence orabsence, or focusing. Details of the image quality will be described ingreater detail below with reference to FIGS. 18 through 22. Imagessatisfying the above-described quality conditions may be stored in theportable photographing apparatus, for example, in operation S160.

FIG. 2 illustrates a portable photographing apparatus, according to anembodiment of the present invention.

The portable photographing apparatus 200 may include an image input unit220, a face detection unit 230, a quality evaluation unit 240, a controlunit 210, a user interface unit 260, and a storage unit 250, forexample.

The image input unit 220 may receive an image from an external imageinput device, for example, such as a camera, and the face detection unit230 may detect a face from the image received from the image input unit220.

The quality evaluation unit 240 may evaluate an image, detected by theface detection unit 230, for example, which may preferably be a stillimage, though embodiments of the present invention are not limitedthereto. The storage unit 250 may store the picture determined as beingan image satisfying predetermined conditions according to the qualityevaluation unit 240.

The user interface unit 260 may allow a user to set a picture mode, forexample, to a moving image mode or a still image mode, to set aphotographing mode to an automatic photographing mode or a manualphotographing mode, or to set an image quality mode, noting thatadditional embodiments are equally available.

The control unit 210 may control operations performed among the imageinput unit 220, the face detection unit 230, the image qualityevaluation unit 240, the user interface unit 260, and/or the storageunit 250 for example.

Herein, the term “unit” is intended to be open to, but is not limitedto, a software and/or hardware component, such as a Field ProgrammableGate Array (FPGA) or Application Specific Integrated Circuit (ASIC),which can perform certain tasks, for example. A module mayadvantageously be configured to reside on an addressable storage mediumand configured to execute on one or more processors. Such a module mayinclude, by way of only an example, components, such as softwarecomponents, object-oriented software components, class components and/ortask components, processes, functions, attributes, procedures,subroutines, segments of program code, drivers, firmware, microcode,circuitry, data, databases, data structures, tables, arrays, andvariables, for example. The functionality provided for in the componentsand modules may be combined into fewer components and modules or furtherseparated into additional components and modules. In addition, thecomponents and modules may be implemented such that they execute one ormore computers in a communication system, again noting that additionalembodiments are available.

In order for a user to photograph a still or moving image, a pictureselection mode, a photographing mode, a quality mode and the like may beset by the user interface unit 260 of the portable photographingapparatus 200.

Here, the picture mode may be a selection mode determining whether amoving image or a still image is to be photographed. For example, thephotographing mode may be a selection mode determining whether a face isto be photographed automatically (automatic photographing mode) ormanually (manual photographing mode). The image quality mode may be aselection mode controlling an evaluation of an illumination condition, aface size, and/or image blurs, adjustment of auto-focusing, andexecution of any or all of these functions.

The respective modes may be offered to a user on a display screen (notshown), for example, embedded in the portable photographing apparatus,and may preferably be provided to a user in a tree structure, notingthat additional embodiments are available. The portable photographingapparatus 200 may similarly include mechanisms for setting any of therespective modes as desired by the user. As only an example, the settingmechanisms may include four-way key buttons, selection buttons, and thelike. In another embodiment of the present invention, all or some of therespective modes may be preprogrammed in the control unit 210 prior tobeing operated, e.g., during a manufacturing stage.

Information corresponding to each of the respective modes input from theuser interface unit 260 may be transferred to the control unit 210, andthe control unit 210 may control the image input unit 220, the facedetection unit 230, the quality evaluation unit 240 and the storage unit250 based on the transferred information.

In a case where the user intends to photograph a still image of aperson, for example, the face detection unit 230 may detect a face fromthe input image received from the image input unit 220 and transfer theinput image to the quality evaluation unit 240. Here, the qualityevaluation unit 240 may determine whether an item selected for qualityevaluation satisfies predetermined criteria, and, if yes, may notify thecontrol unit 210.

In an automatic photographing mode, the control unit 210 may control thephotographing of the corresponding image to be photographedautomatically and store the photographed image in the storage unit 250.In a manual photographing mode, the control unit 210 may notify the userof the set mode, in a predetermined manner, and when the user manuallyphotographs the corresponding image by a predetermined method, thecontrol unit 210 may then control the corresponding image to be storedin the storage unit 250. Here, the predetermined method may include, forexample, a visual display mechanism such as an LED, an alarm, and so on,noting that additional embodiments are equally available.

When the user intends to photograph a moving image of person, forexample, the face detection unit 230 may detect a face from the inputimage received from the image input unit 220, transfer the detected faceimage to the quality evaluation unit 240, or directly store the same inthe storage unit 250. Here, since evaluation of all of the above-statedevaluation items may cause a disconnection of the face image, onlyauto-focusing adjustment may preferably be evaluated in this stage.

Alternatively, the control unit 210 may perform the auto-focusingoperation on the still or moving image.

A face detection method, performed by the face detection unit 230, willnow be described with greater detail with reference to FIGS. 3 through17.

To detect a face, it is beneficial to determine and define face rotationangles available to people.

As shown in FIG. 3, a face may be rotated around, for example,three-dimensional coordinate axes, e.g., an X-axis, a Y-axis, and aZ-axis.

When the face is rotated around the X-axis, an up-view, a frontal-view,and a down-view may be defined.

When the face is rotated around the Y-axis, a left-view, a frontal-view,and a right-view may be defined.

When the face is rotated around the Z-axis, views may be discriminatedaccording to a leaning angle. As illustrated in FIG. 3, the face maylean at intervals of 30 degrees, noting that this selection has beenchosen for simplicity in explanation and additional embodiments areavailable.

Thus, for explanation of embodiments of the invention, rotation anglesavailable to people will be described with respect to each of the X-,Y-, and Z-axes, again noting that an alternative coordinate system mayalso be available.

FIG. 4 illustrates rotation angles of a face around the X-axis. Here,rotation around the X-axis, i.e., X-rotation, may be referred to as“nodding rotation” or “out-of-plane rotation.” The X-rotation (i.e.,up-and-down nodding) may have a range of about [−60°, 80°], for example.However, an up-view face in a range of [20°, 50°] also has a highoccurrence frequency and may be detected by a method of detecting afrontal-view face, for example. It has been found that an up-view facein a range of [50°, 80°] may rarely occur and may not show face elementswell, and thus, may be thus excluded from detection. With respect to theX-rotation, thus, only a down-view face in a range of [−60°, −20°] and afrontal-view face in a range of [−20°, 50°] may detected, in anembodiment of the present invention. In the case of photographing astill image, only a frontal-view face in a range of [−20°, 20°] may bedetected, according to another embodiment of the present invention.

FIG. 5 illustrates rotation angles of a face around the Y-axis. Rotationaround the Y-axis, i.e., Y-rotation, will be referred to as“out-of-plane rotation.”

The Y-rotation (left and right rotation) may have a range of [−180°,180°]. However, in a range of [180°, −90°] and a range of [90°, 180°],the back of a head would occupy more of the image than a face.Accordingly, in an embodiment of the present invention, only a left-viewface in a range of [−90°, −20°], a frontal-view face in a range of[−20°, 20°], and a right-view face in a range of [20°, 90°] are detectedwith respect to the Y-rotation. In a case of photographing a stillimage, only a frontal-view face in a range of [−20°, 20°] may bedetected, according to another embodiment of the present invention.

When a face is rotated around the Z-axis, Z-rotation (left and rightleaning) has a range of [−180°, 180°]. Here, the Z-rotation will bereferred to as “in-plane rotation.”

With respect to Z-rotation, all rotation in the range of [−180°, 180°]may be dealt with. However, people usually only lean their faces in arange of [−45°, 45°] when standing. Accordingly, detection may beperformed with respect to rotation in the range of [−45°, 45°] in abasic mode, and performed with respect to rotation in the range of[−180°, 180°] in an extension mode, according to an embodiment of thepresent invention.

In addition, with respect to the Z-rotation, a face may be defined asleaning according to intervals of 30° and 45°, which are respectivelyillustrated in FIGS. 6A and 6B.

Hereinafter, a mode illustrated in FIG. 6A may be referred to as a firstZ-rotation mode and a mode illustrated in FIG. 6B may be referred to asa second Z-rotation mode, noting that additional embodiments are equallyavailable.

In the Z-rotation, a left-leaning face, an upright face, and aright-leaning face may be defined.

Accordingly, Table 1 below shows ranges of rotation angles of a face tobe detected, according to an embodiment of the present invention.

TABLE 1 Division X-rotation Y-rotation Z-rotation DescriptionUp-and-down Left and right Left and right nodding rotation leaningRotatable angte [−60°, 80°] [−180°, 180°] [−180°, 180°] Detection Basic[−60°, 50°] [−90°, 90°] [−45°, 45°] mode target Extension [−60°, 50°][−90°, 90°] [−180°, 180°] mode

Meanwhile, the face detection unit 230, according to an embodiment ofthe present invention, may detect a face using cascaded classifiers,each of which is trained with conventional appearance-based patternrecognition, i.e., an AdaBoost algorithm. The AdaBoost algorithm is avery efficient learning algorithm that configures a plurality of simpleand fast weak classifiers in a form of a weighted sum, thereby producinga single strong classifier which is fast and has a high success rate.Hereinafter, a strong classifier for detecting a particular face posewill be referred to as a “face detector.”

The face detector, thus, may discriminate a face from a non-face in aninput image using a plurality of learned face patterns. It may also benecessary to determine face patterns to be learned.

As described above, to detect a down-view face in the range of [−60°,−20°] and a frontal-view face in the range of [−20°, 50°], with respectto the X-rotation, two face detectors may be needed.

In addition, to detect a left-view face in the range of [−90°, −20°], afrontal-view face in the range of [−20°, 20°], and a right-view face inthe range of [20°, 90°] with respect to the Y-rotation, three facedetectors may be needed.

In the aforementioned first Z-rotation mode, 12 face detectors may beneeded in the extension mode and three face detectors may be needed inthe basic mode. In the aforementioned second Z-rotation mode, 8 facedetectors may be needed in the extension mode and two face detectors maybe needed in the basic mode.

Consequently, when all of the X-, Y-, and Z-rotations are considered inthe first Z-rotation mode, 2×3×3=18 face detectors may be needed in thebasic mode and 2×3×12=72 face detectors may be needed in the extensionmode.

When all of the X-, Y-, and Z-rotations are considered in the secondZ-rotation mode, 2×3×2=12 face detectors may be needed in the basic modeand 2×3×8=48 face detectors may be are needed in the extension mode.

However, in the first and second Z-rotation modes, the number of facedetectors for learning can be reduced, according to an embodiment of thepresent invention, by using rotation or mirroring (changing left andright coordinates), as illustrated in FIG. 7.

For example, with respect to a frontal-view face in the first Z-rotationmode, when an upright face 702 is rotated by −90°, 90°, and 180°, faceimages 708, 720, and 714 can be obtained. When a 300 left-leaning face724 is rotated by −90°, 90°, and 180°, face images 706, 718, and 712 canbe obtained. In addition, when the 30° left-leaning face 724 ismirrored, a 30° right-leaning face 704 can be obtained. When the 30°right-leaning face 704 is rotated by −90°, 90°, and 180°, face images710, 722, and 716 can be obtained. As a result, since faces, other thanthe upright face 702 and the 30° left-leaning face 724, can be obtainedthrough rotation or mirroring, 12 face detectors for a frontal-view facemay be obtained by learning merely two face detectors, according to anembodiment of the present invention.

In a similar manner, as shown in FIG. 8, 12 face detectors may beobtained using three face detectors with respect to a left-view face. Inaddition, a right-view may be obtained by mirroring the left-view face.

Consequently, when all of the X-, Y-, and Z-rotations are considered inthe first Z-rotation mode, 2 (a frontal-view and a down-view)×5=10 facedetectors may be needed to be learned in the basic and extension modes.Here, faces to be learned, with respect to the frontal-view face, areshown in FIG. 9.

FIG. 10 illustrates a procedure for reducing the number of facedetectors necessary for learning in the second Z-rotation mode for afrontal-view face, according to an embodiment of the present invention.

Referring to FIG. 10, with respect to a frontal-view face in the secondZ-rotation mode, when a right-leaning face 1002 in the basic mode isrotated by −90°, 90°, and 180°, face images 1006, 1014, and 1010 can beobtained. When the right-leaning face 1002 is mirrored, a left-leaningface 1016 can be obtained. When the left-leaning face 1016 is rotated by−90°, 90°, and 180°, face images 1004, 1012, and 1008 can be obtained.Consequently, when only the right-leaning face 1002 is learned, otherfaces may be obtained through rotation or mirroring. Accordingly, 8 facedetectors for the frontal-view face may be obtained by learning only asingle face detector, according to an embodiment of the presentinvention.

In a similar manner, referring to FIG. 11, 8 face detectors may beobtained using two face detectors with respect to a left-view face. Inaddition, a right-view face may be obtained by mirroring the left-viewface.

Consequently, when all of the X-, Y-, and Z-rotations are considered inthe second Z-rotation mode, 2 (a frontal-view and a down-view)×3=6 facedetectors may be needed to learn in the basic and extension modes. Here,faces to be learned, with respect to the frontal-view face, are shown inFIG. 12.

Accordingly, Table 2 below shows the number of face detectors needed,according to an embodiment of the present invention.

TABLE 2 Number of necessary Number of face face detectors detectors tolearn First Z Basic mode 18 10 mode Extension mode 72 10 Second Z Basicmode 12 6 mode Extension mode 48 6

FIG. 13 illustrates a face detection unit 230, according to anembodiment of the present invention.

The face detection unit 230 may include a face detection control module231, a subwindow generation module 232, a first face search module 233,a second face search module 234, and a third face search module 235.Here, the ‘module’ can be interpreted similarly to the above-describedmeaning of ‘unit’.

The subwindow generation module 232 may generate a subwindow for aninput image received from the image input unit 220. Here, the subwindowcan be an image obtained by dividing the input image into apredetermined size. When the input image has a size of 320×240 (pixels),for example, the input image may be divided according to a 24×24(pixels) size, so that the divided image becomes a subwindow of theinput image. Here, the subwindow generation module 232 may define aminimum subwindow size, and sequentially supply the generated subwindowto the first face search module 233, while gradually increasing atransverse and/or longitudinal subwindow size starting from the minimumsubwindow size, for example.

The first face search module 233, the second face search module 234, andthe third face search module 235 may perform face detection fordetecting a face from subwindows generated by the subwindow generationmodule 232.

The face detection control module 231 may control the operation of thesubwindow generation module 232 associated with the operations of thefirst through third face search modules 233-235, for example.

When the first face search module 233 receives a subwindow from thesubwindow generation module 232, the first search module 233 may detecta face from the subwindow using a predetermined algorithm. If a face isdetected, the first face search module 233 may transfer the subwindow tothe second face search module 234. If no face is detected, the user maymanipulate the face detection control module 231 to control thesubwindow generation module 232, for example, to generate a newsubwindow to be transferred to the first face search module 233.

The second face search module 234 may detect a face from the transferredsubwindow using a predetermined algorithm, for example. If a face isdetected, the second face search module 234 may transfer the subwindowto the third face search module 235. If no face is detected, the usermay manipulate the face detection control module 231 to control thesubwindow generation module 232, for example, to generate a newsubwindow to be transferred to the first face search module 233.

The third face search module 235 may detect a face from the transferredsubwindow using a predetermined algorithm. Again, if a face is detected,the third face search module 235 transfers an image of the detected faceto the quality evaluation unit 240. When a moving image is photographed,the detected face image may be stored directly in the storage unit 250by way of the control unit 210 without being transferred to the qualityevaluation unit 240.

If no face is detected by the third face search module 235, the user maymanipulate the face detection control module 231 to control thesubwindow generation module 232, for example, to generate a newsubwindow to then be transferred to the first face search module 233.

Meanwhile, the respective face detection algorithms for the firstthrough third search modules 233-235 will now be described in greaterdetail with reference to FIGS. 14A through 14C.

Accordingly, FIG. 14A illustrates a conventional coarse-to-fine searchalgorithm, FIG. 14B illustrates a conventional simple-to-complex searchalgorithm, and FIG. 14C illustrates a parallel-to-separated searchalgorithm, according to an embodiment of the present invention.

In the coarse-to-fine search algorithm, a whole-view classifier may beobtained at an initial stage of a cascaded classifier and thenclassifiers for gradually decreasing angles may be obtained. When thecoarse-to-fine search algorithm is used, a non-face subwindow may bequickly removed in the early stages so that an entire detection time canbe reduced. The whole-view classifier may only search for the shape of aface in a given subwindow using information that has been learned,regardless of the pose of the face.

In the simple-to-complex search algorithm, an easy and simple classifiermay be disposed at an earlier stage and a difficult and complexclassifier may be disposed at a latter stage to increase speed. Sincemost of non-faces subwindows can be removed in an initial stage, such abeneficial time savings effect can be achieved when the initial stage ismade simple.

In the parallel-to-separated search algorithm, according to anembodiment of the present invention, face detectors for all directionsmay be arranged in parallel up to, for example, K-th stages, and facedetectors for respective different directions may be independently andseparately, for example, arranged starting from a (K+1)-th stage. In theparallel arrangement, when face detection succeeds in one direction, asubsequent stage in the same direction may be continued. However, whenface detection fails in one direction, face detection may be performedin a different direction. In the separated arrangement, when facedetection in one direction succeeds, a subsequent stage in the samedirection may be continued. However, when face detection fails, anon-face determination may be immediately determined and the facedetection terminated. When the parallel-to-separated search algorithm isused, the direction of a face in an input image may be determined duringan initial stage, and thereafter, a face or a non-face determination,only with respect to the direction, may be made. Accordingly, accordingto embodiments of the present invention, face detectors having highaccuracy and fast speed can be implemented.

When the algorithms illustrated in FIGS. 14A through 14C are combined, amulti-view face detector, illustrated in FIG. 15, can be obtained.

In FIG. 15, each illustrated block represents a face detector detectinga face in a direction written in the block. The area denoted by “A”operates in a similar manner as blocks to its left, and thus adescription thereof is omitted. Downward arrows indicate the flow of anoperation when a face detector succeeds in detecting a face, andrightward arrows indicate the flow of an operation when a face detectorfails in detecting a face. These arrow designations are similar todesignations presented in FIGS. 14A-14C.

As an example of such sequential operation, upon receiving a subwindowfrom the subwindow generation module 232, the first face search module233 may discriminate whether the subwindow includes a face using awhole-view face detector based on already learned information in stage1˜1′.

When the presence of a face is determined in stage 1˜1′, the first facesearch module 233 transmits the subwindow to the second face searchmodule 234. The second face search module 234 may then sequentiallyperform stages 2˜2′ and 3˜4.

In stage 2˜2′, a frontal-view face and a down-view face may be definedwith respect to the X-rotation and face detection may be performed basedon the already learned information. In stage 3˜4, an upright face, aleft-leaning face, and a right-leaning face may be defined with respectto the Z-rotation and face detection may be performed based on thealready learned information.

Here, stage 1˜1′, stage 2˜2′, and stage 3˜4 may be performed using thecoarse-to-fine search algorithm. Face detectors performing stage 1˜1′,stage 2˜2′, and stage 3˜4 may internally use the simple-to-complexsearch algorithm.

Up to stage M, faces in all directions may be defined based on thealready learned information. Here, up to stage K, when face detectionsucceeds, a subsequent downward stage may be performed, and when facedetection fails, the operation may shift to a right face detector, forexample. After stage K, when face detection succeeds, a subsequentdownward stage may be performed, but when face detection fails, anon-face determination may be made and face detection on a currentsubwindow may be terminated. Accordingly, only with respect to asubwindow reaching stage M, can the presence of a face be determined.

Stage 5˜K and stage K+1˜M may be performed using theparallel-to-separated search algorithm. In addition, face detectorsperforming stage 5˜K and stage K+1˜M may internally use thesimple-to-complex search algorithm.

FIGS. 16A and 16B illustrate a detecting of a face, according to anembodiment of the present invention. FIG. 17 illustrates another method,according to the embodiment illustrated in FIGS. 16A and 16B.

A corresponding method of detecting a face, according to an embodimentof the present invention, will now be described with more detail withreference to FIGS. 16A through 17. For sake of clarity and ease ofexplanation, it will be assumed herein that an image provided by theimage input unit 220 is a frontal-view face defined with respect to theX-rotation. Accordingly, stage 2˜2′ shown in FIG. 15 may be omitted, anda stage for detecting a whole-view face will be referred to as stage1˜2.

In FIG. 17, the illustrated W represents “whole-view,” U represents“upright”, L represents “30° left-leaned”, R represents “30°right-leaning”, “f” represents “fail” indicating that face detection hasfailed, “s” represents “succeed” indicating that face detection hassucceeded, and NF represents a “non-face” determination.

When the subwindow generation module 232 generates a subwindow, inoperation S1602, an initial value for detecting a face in the subwindowis set, in operation S1604. The initial value includes parameters n, N₁,N₂, K, and M.

Here, the parameter “n” indicates a stage in the face detection, theparameter N₁ indicates a reference value for searching for a whole-viewface, the parameter N₂ indicates a reference value for searching for anupright-view face, and a left-leaning view face and a right-leaning viewface defined with respect to the Z-rotation. The parameter M indicates areference value for searching for a frontal-view face, a left-view face,and a right-view face defined with respect to the Y-rotation, and theparameter K indicates a reference value for discriminating a stage forarranging face detectors separately from a stage for arranging facedetectors in parallel, in the parallel-to-separated search algorithm,according to an embodiment of the present invention. Here, the initialvalue may be set such that n=1, N₁=2, N₂=4, K=10, and M=25, according toan embodiment of the present invention.

After the initial value is set, the first face search module 233 maydetect a whole-view face in stage “n,” in operation S1606, i.e.,operation 1702. If a whole-view face is not detected, it may bedetermined that no face exists in the subwindow. If a whole-view face isdetected, the parameter “n” is increased by 1, in operation S1608.Whether the value of “n” is greater than the value of N₁ is thendetermined, in operation S1610. If the value of “n” is not greater thanthe value of N₁, the method goes back to operation S1606. Since theparameter N₁ may be set to 2, in the embodiment of the presentinvention, the first face search module 233 may perform thesimple-to-complex search algorithm on the whole-view face one time(1702→1704).

If the value of “n” is determined to be greater than the value of N₁, inoperation S1610, the second face search module 234 performs a anupright-view face detection in stage “n”, in operation S1612 (i.e.,operation 1706). Here, the coarse-to-fine search algorithm may be used.

If the upright-view face is not detected in operation S1612 (i.e.,operation 1706), a left-leaning viewface is detected in the same stage“n”, in operation S1660 (i.e., operation 1708). If the left-leaning viewface is not detected in operation S1660, a right-leaning view face maybe detected in the same stage “n”, in operation S1670 (i.e., operation1710). If the right-leaning view face is not detected in operationS1670, it is determined that no face exists in the current subwindow. Ifa face is detected in operations S1612 (1706), S1660 (1708), or S1670(1710), the value of “n” is increased by 1, in operations S1614, S1662,or S1672, respectively, and it is determined whether the increased valueof “n” is greater than the value of N₂, in operations S1617, S1664, orS1674, respectively. If the value of “n” is not greater than the valueof N₂, the method goes back to operation S1612, S1660, or S1670. Sincethe value of N₂ is set to 4, according to an embodiment of the presentinvention, the second face search module 234 performs thesimple-to-complex search algorithm on the upright-view face, theleft-leaning view face, or the right-leaning view face one time(operations 1706→1712, 1708→1714, or 1710→1716).

Hereinafter, solely for clarity of the description, it will be assumedthat a face is detected in operation S1612 and the value of “n” isgreater than the value of N₂ in operation S1616. Referring to FIG. 16B,the same operations as operations S1620 through S1654 may be performedin an I-block (S1666) and an II-block (S1676).

The third face search module 235 may detect an upright frontal-view facein stage “n”, in operation S1620 (i.e., operation 1718). If the uprightfrontal-view face is not detected in operation S1620 (1718), an uprightleft-leaning view face may be detected in the same stage “n”, inoperation S1626 (i.e., operation 1720). If the upright left-leaning viewface is not detected in operation S1626, an upright right-leaning viewface may be detected in the same stage “n”, in operation S1632 (i.e.,operation 1722). If the upright right-leaning view face is not detectedin operation S1632, face detection may be continued in the I-block(S1666) or the II-block (S1676).

If a face is detected in operations S1620(1718), S1626(S1720), orS1632(1722), the value of “n” is increased by 1, in operations S1622,S1628, or S1634, respectively, and it is determined whether theincreased value of “n” is greater than the value of K, in operationsS1624, S1630, or S1635, respectively. If the value of “n” is not greaterthan the value of K, the method goes back to operations S1620, S1626, orS1632. Since the value of K may be set to 10, in an embodiment of thepresent invention, the third face search module 235 performs thesimple-to-complex search algorithm on the upright frontal-view face, theupright left-leaning view face, or the upright right-leaning view face,up to a maximum of 5 times (1718→1724, 1720→1726, or 1722→1728).

Hereinafter, for clarity of the description, it will be assumed that theupright frontal-view face is detected in operation S1620 and that thevalue of “n” is determined to be greater than the value of K.

The third face search module 235 may detects an upright frontal-viewface in stage “n”, in operation S1640 (S1730). If the uprightfrontal-view face is not detected in operation S1640 (S1730), it isdetermined that no face exists in the current subwindow. If the uprightfrontal-view face is detected in operation S1640, the value of “n” isincreased by 1 in operation S1642 and whether the increased value of “n”is greater than the value of M may be determined, in operation S1644. Ifthe increased value of “n” is not greater than the value of M, themethod goes back to operation S1640. If the increased value of “n” isgreater than the value of M, a face will be determined as existing inthe current subwindow.

As described above, the third face search module 235 may operate usingthe parallel-to-separated search algorithm, according to an embodimentof the present invention, and the conventional simple-to-complex searchalgorithm. In other words, face detectors for all directions may bearranged in parallel up to stage K and may be arranged separately fromeach other from stage K+1 to stage M, and the simple-to-complex searchalgorithm may be used when a stage shifts.

Meanwhile, in an embodiment of the present invention, X-rotation facesmay be detected first, Z-rotation faces may be detected next, andY-rotation faces may be detected finally. However, such order is just anexample, and it will be obvious to those skilled in the art that theorder may be changed in face detection.

According to an embodiment of the present invention, in a case ofphotographing a still image, only a frontal-view face in a range of[−20°, 20°] may be detected with respect to the X-rotation, Y-rotation,and Z-rotation in the above-described face detection method. Thus, thecontrol unit 210 may control the face detection control module 231 tooperate only a face detector that detects faces in the range of [−20°,20°].

FIG. 18 illustrates a still face image photographing process, accordingto an embodiment of the present invention.

In order to photograph a still image, when a user selects a still imagemode, e.g., through the user interface unit 260 shown in FIG. 2, theface detection unit 230 may detect a face from the input image receivedfrom the image input unit 220, in operation S1802. Here, face detectionmay be performed using a face detector that detects only a frontal-viewface in a range of [−20°, 20°] with respect to the X-rotation,Y-rotation and Z-rotation.

If the face detection unit 230 succeeds in face detection, the proceduremay proceed to an image quality evaluation operation (S1804-→S1806), andif not, a face may be detected from the next image (operationsS1804-→S1802).

When the user selects illumination intensity as an evaluation item inthe image quality selection mode, e.g., provided in the user interfaceunit 260, the illumination intensity may be evaluated (operationsS1806-→S1808). If the evaluated illumination intensity is determined asbeing appropriate, the procedure proceeds to a subsequent operation(S1810-→S1812), and if not, a face may be detected from the next image(operations S1810-→S1802).

The illumination intensity may be evaluated in the following manner.When image illumination intensity v is greater than a predeterminedcritical image illumination intensity V*, the image may be stored.

In this case, the illumination intensity v may be defined as an overallaverage of an image I having a dimension of W*H and expressed by:

$\begin{matrix}{{v(I)} = \frac{\sum\limits_{i = 1}^{W}{\sum\limits_{j = 1}^{H}{I( {i,j} )}}}{W \times H}} & (1)\end{matrix}$

Here, W represents a width of an image H represents a height of theimage I, i and j represent indices of numbers of pixels for W and H,respectively, and I(i, j) represents illumination intensity atcoordinates (i, j) of the image I.

When the user selects a face size as an evaluation item in the imagequality selection mode, e.g., provided in the user interface unit 260, aface size may be evaluated (operations S1812->S1814). If the face sizeis determined as being appropriate, the procedure proceeds to asubsequent operation (S1816-→S1818), and if not, a face may be detectedfrom the next image (operations S1816-→S1802). Methods of measuring theface size and determining whether the evaluated face size is appropriateor not, will be described in more detail below with reference to FIG.20.

When the user selects a presence of image blurs as an evaluation item inthe image quality selection mode, e.g., provided in the user interfaceunit 260, the presence of image blurs is evaluated (operationsS1818-→S1820). If no image blur exists, the procedure proceeds to asubsequent operation (S1822-→S1824), and if not, a face may be detectedfrom the next image (operations S1822-→S1802). A method of examiningpresence of blurs will be described in more detail below with referenceto FIGS. 21 and 22.

When the user selects auto-focusing as an evaluation item in the imagequality selection mode, e.g., provided in the user interface unit 260,auto-focusing, may be performed (operations S1824-→S1826). Here, a focusmay be adjusted according to the center of the face, for example.

When the user selects automatic photographing as the photographing mode,e.g., provided in the user interface unit 260, the control unit 210 maystore the current frame in the storage unit 250 (operationsS1828-→S1834). On the other hand, when the user selects a manualphotographing mode, the control unit 210 may notify the user of theselected mode, e.g., by a predetermined method, in operation S1830. Whenthe user photographs the corresponding image manually, the control unit210 may store the image in the storage unit 250, in operation S1832. Inthis case, the control unit 210 may control the corresponding image tobe stored in the storage unit 250, for example. Here, the predeterminedmethod may include a visual display mechanism, such as an LED, an alarm,and so on, for example.

FIG. 19 illustrates a motion face image photographing process, accordingto an embodiment of the present invention.

In order for a user to photograph a moving image, when the user selectsa moving image mode, e.g., through the user interface unit 260 shown inFIG. 2, the face detection unit 230 may detect for a face from the imagereceived from the image input unit 220, in operation S1902. Here, theface detection unit 230 may employ a multi-view face detector. If theface detection unit 230 succeeds in face detection, a frame of thedetected image may be stored (operations S1904-→S1906), and if not, aface may be detected from the next image (operations S1904-→S1902). Theframe stored in operation S1906 may be the first frame of a to-be-storedmoving image, for example.

In order to obtain a second frame of the picture frame and framesfollowing the second frame, a face may be detected from the imagereceived by the image input unit 220 using the multi-view face detector,in operation S1908. If the face detection is successful, anauto-focusing function may be performed (operations S1910-→S1914), thecurrently detected image frame may be stored, in operation S1916. Theperforming of the auto-focusing function may prevent an abrupt change inthe focus due to other objects or matter appearing on the picture image.If it is determined, in operation S1910, that the face detection is notsuccessful, it is determined whether a number of face detection fails issmaller than a predetermined number K, in operation S1912. If the numberof face detection fails is smaller than the predetermined number K, thecurrent frame may be stored, in operation S1916. In other words, even ifno face is detected from the frame, the first frame may have alreadybeen stored, in operation S1906, which means that storing of the movingimage has already started. Thus, in order to prevent the stored movingimage from being disconnected, the corresponding frame may be storedeven if the face detection fails a predetermined number of times. Here,the value of K may preferably be in a range of 10-15, and a timecorresponding thereto may preferably range from about 0.5 to about 1second. If it is determined in operation S1912 that the number of facedetection fails is not smaller than the predetermined number K, storingof the moving image may be terminated.

If the user forcibly presses a button to terminate photographing, in themiddle of photographing the moving image or where a photographing timeexceeds a preset recording time of the moving image, storing of themoving image may be terminated. Otherwise, face detection may beperformed on the next image frame using the multi-view face detector, inoperation S1918. For example, assuming that the user sets a maximumrecording time T to 5 minutes, if the storage time exceeds 5 minutes,the photographing is automatically terminated.

FIG. 20 illustrates in portions (a) and (b) a picture image view showingexamples of detecting face sizes, according to an embodiment of thepresent invention.

To evaluate a face size, it will be assumed herein that if a face size(w, h) in the detected image is greater than a preset critical size (W*,H*), the face size (w, h) may be determined to be an appropriate size.In this case, face size (w, h), in which w denotes a width and h denotesa height, represents a size of a region indicating a face in thedetected image.

FIG. 21 illustrates a detecting of blurs, according to an embodiment ofthe present invention.

A portable photographing apparatus may perform face detection using aface detector, in operation S2110, and then extract an image of thedetected face image, in operation S2120. Here, image conversion may beperformed using a 2-D DCT (two-dimensional Discrete Cosine Transform)algorithm, in operation S2130, and a value “p” representing a spatialfrequency proportion may be obtained based on information about theconverted image, in operation S2140. If the value “p” is greater than apreset spatial frequency critical proportion P then existence of blursmay determined, in operation S2150.

FIG. 22 illustrates a picture image view showing an example of detectingblurs, according to an embodiment of the present invention.

In FIG. 22, portion (a) shows a case where the value “p” is greater thanP indicating that no blur exists in the picture image, and portion (b)shows a case where the value “p” is smaller than P indicating that blursexist in the picture image.

According to embodiments of the present invention, when a userphotographs a still image, the portable photographing apparatus mayautomatically detect a location of a face to notify the user of anappropriate photographing state, thereby enabling the user to obtain animproved quality still image.

In addition, when the user photographs a moving image, the moving imagemay be stored only when a face is detected, thereby extending the timeduring which all moving images may be stored.

Embodiments of the present invention have been described with at leastreference to flowchart illustrations of methods. It will be furtherunderstood that each block of the flowchart illustrations, andcombinations of blocks in the flowchart illustrations, can beimplemented by computer readable code. The computer readable code can beprovided to a processor of a general purpose computer, special purposecomputer, or other programmable data processing apparatus to produce amachine, such that the code, which execute via the processor of thecomputer or other programmable data processing apparatus, are forimplementing the operations specified in the flowchart block or blocks,for example. The computer readable code may also be stored in a medium,e.g., a computer usable or computer-readable memory, that can includedirections for a computer or other programmable data processingapparatus to function in a particular manner, such that the code storedin the medium produces an article of manufacture to implement theoperations specified in the flowchart block or blocks. The computerreadable code may also be loaded onto a computer or other programmabledata processing apparatus, for example, to cause a series of operationsto be performed on the computer or other programmable apparatus, forexample, to produce a computer implemented process such that theinstructions that execute on the computer or other programmableapparatus include elements to implement the operations specified in theflowchart block or blocks.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A portable photographing apparatus, comprising: a face detection unitto search for a face in a received image and identify a correspondingdetected face in the received image; a storage unit to store thereceived image, upon the face detection unit identifying the detectedface in the received image, as a moving image in a first mode; and aquality evaluation unit to evaluate a quality of the received image andto store the received image as a still image in a second mode upon theface detection unit identifying the detected face in the received imageand a satisfaction of a selective predetermined condition evaluatedbased on a quality evaluation of the received image.
 2. The portablephotographing apparatus of claim 1, further comprising an image inputunit to receive the image as the received still image.
 3. The portablephotographing apparatus of claim 1, wherein the quality evaluation unitevaluates an illumination condition of the received image.
 4. Theportable photographing apparatus of claim 1, wherein the qualityevaluation unit evaluates a face size of the received image.
 5. Theportable photographing apparatus of claim 1, wherein the qualityevaluation unit evaluates an image blur state of the received image. 6.The portable photographing apparatus of claim 1, wherein the qualityevaluation unit causes a focusing to be adjusted on the face in thereceived image as detected by the face detection unit.
 7. The portablephotographing apparatus of claim 1, further comprising a user interfaceunit to provide for a user interface to allow a user to select a movingimage mode or a still image mode.
 8. The portable photographingapparatus of claim 1, further comprising a user interface unit toprovide for a user interface to allow a user to select an automaticphotographing mode or a manual photographing mode for when the face isdetected.
 9. The portable photographing apparatus of claim 1, furthercomprising a user interface unit to provide for a user interface toallow a user to select an image quality characteristic to be implementedfor the quality evaluation.
 10. A portable photographing apparatus,comprising: a face detection unit to detect a face from a receivedimage; a storage unit to store the received image upon detection of theface as a moving image in a first mode; a quality evaluation unit toevaluate a quality of the received image and to store the received imageas a still image in a second mode upon a satisfaction of a selectivepredetermined condition evaluated based on a quality evaluation of thereceived image; and an image input unit to receive the image as thereceived still image, wherein the face detection unit comprises: asubwindow generation module to receive an image from the image inputunit and generate a subwindow corresponding to the received image; afirst face search module to receive the subwindow from the subwindowgeneration module and to detect a face from the subwindow to determinewhether a frontal-view face exists; a second face search module to, ifthe frontal-view face is detected by the first face search module,sequentially detect two mode faces among a first mode face generated byup and down facial rotation, a second mode face made by a leaning of ahead to either side of left and right sides, and a third mode face madeby left and right facial rotation; and a third face search module todetect a remaining mode face not detected by the second face searchmodule.
 11. The portable photographing apparatus of claim 10, whereinthe face detection unit further comprises: a face detection controlmodule to generate a new subwindow to be supplied to the first facesearch module if no face is detected by any of the first face searchmodule, the second face search module, or the third face search module.12. The portable photographing apparatus of claim 10, wherein the thirdface search module sequentially performs an operation of arranging facedetectors for all directions in parallel, and when succeeding in facedetection in one direction performing face detection in a same directionusing a more complex face detector, and when failing in face detectionin one direction performing face detection in a different direction, andan operation of independently and separately arranging the facedetectors for all directions, such that when succeeding in facedetection in one direction performing face detection in a same directionusing a more complex face detector, and when failing in face detectiondetermining that a face is not detected from the input image.
 13. Theportable photographing apparatus of claim 10, wherein the second facesearch module performs sequential detection of the two mode faces usinga coarse-to-fine search algorithm.
 14. The portable photographingapparatus of claim 10, wherein the second face search module attemptsdetection of one of the two mode faces using a simple-to-complex searchalgorithm.
 15. A method of photographing a picture in a portablephotographing apparatus based on face detection, the method comprising:receiving an image; performing a detection for a face in the receivedimage and identifying a corresponding detected face in the receivedimage; and storing the received image having the detected face, basedupon the performing of the detection for the face in the received image,as a moving image in a first mode, and evaluating the quality of thereceived image having the detected face and storing the received imagehaving the detected face as a still image in a second mode uponsatisfaction of a selective predetermined condition evaluated based on aquality evaluation of the received image.
 16. The method of claim 15,wherein the selective predetermined condition is an illuminationcondition of the received image.
 17. The method of claim 15, wherein theselective predetermined condition is a face size of the received image.18. The method of claim 15, wherein the selective predeterminedcondition is an image blur state of the received image.
 19. The methodof claim 15, wherein the selective predetermined condition is focusingadjustment performed on the face in the received image.
 20. The methodof claim 15, further comprising providing a user interface to allow auser to select a moving image mode or a still image mode.
 21. The methodof claim 15, further comprising providing a user interface to allow auser to select an automatic photographing mode or a manual photographingmode for the face detection.
 22. The method of claim 15, furthercomprising providing a user interface to allow a user to select an imagequality condition for the predetermined condition.
 23. At least onenon-transitory medium comprising computer readable code to implement themethod of claim
 15. 24. A method of photographing a picture in aportable photographing apparatus based on face detection, the methodcomprising: receiving an image; detecting a face from the receivedimage; and storing the received image detected by the face detectionunit as a moving image in a first mode, and evaluating the quality ofthe received image detected by the face detection unit and storing thereceived image as a still image in a second mode upon satisfaction of aselective predetermined condition evaluated based on a qualityevaluation of the received image, wherein the detecting of the facecomprises: sequentially selectively detecting two mode faces among afirst mode face generated by up and down facial rotation, a second modeface generated by a leaning of a head to either side of left and rightsides, and a third mode face made by left and right facial rotation;detecting a remaining mode face that is not detected in the sequentiallydetecting of the two faces; and if the remaining mode face is detectedin the detecting of the remaining mode face, determining that the faceis detected in the image, wherein the detecting of the remaining modeface comprises arranging face detectors for all directions in parallelto perform face detection, and independently and separately arrangingthe face detectors for all directions to perform face detection.
 25. Themethod of claim 24, wherein in the parallel arranging of the facedetectors, when succeeding in face detection in one direction facedetection is performed in a same direction using a more complex facedetector, and when failing in face detection in one direction facedetection is performed in a different direction.
 26. The method of claim24, wherein in the independently and separately arranging of the facedetectors, when succeeding in face detection in one direction facedetection is performed in a same direction using a more complex facedetector, and when failing in face detection non- detection of a face isdetermined for the received image.
 27. The method of claim 24, whereinthe sequentially detecting of the two mode faces comprises sequentiallydetecting the two mode faces using a coarse-to-fine search algorithm.28. The method of claim 24, wherein the sequentially detecting of thetwo mode faces comprises sequentially detecting one of the two modefaces using a simple-to-complex search algorithm.
 29. An imagingapparatus, comprising: a face detection unit to detect a face from areceived image through a multilayer face detection scheme, with thedifferent layers of face detection separately detecting for a particularpotential orientation of a face in the received image and with thedifferent layers of face detection being implemented with a number offace orientation detectors for a successful face detection less than allavailable face detectors respectively for a number of particularpotential face orientations in the received image; and a storage unit toselectively store the received image based upon a detection of the faceby the different layers of face detection.
 30. The apparatus of claim29, wherein plural of the different layers of face detection aresequenced such that a subsequent layer of face detection is implementedafter a current layer of face detection is successful, and upon thecurrent layer of face detection being unsuccessful a different layer offace detection from the subsequent layer of face detection and thecurrent layer of face detection is implemented.
 31. A portablephotographing apparatus, comprising: a face detection unit to detect aface from a received image after a determination that the face exists inthe received image; a storage unit to selectively store the receivedimage based upon detection of the face as a face detection moving imageor a face detection still image, wherein the selective storing of thereceived image as the face detection still image is based upon a qualityevaluation of the received image; and a quality evaluation unit toperform the quality evaluation based on a certain aspect of thedetection of the face, after the detection of the face, of the receivedimage and to store the received image in the selective storing by thestorage unit as the face detection still image upon a satisfaction of aselective predetermined condition evaluated based on the qualityevaluation of the received image.
 32. The portable photographingapparatus of claim 31, further comprising: a notification unit to notifya user of the quality evaluation of the received image.
 33. The portablephotographing apparatus of claim 32, wherein the notification unitnotifies by visual display mechanism.
 34. The portable photographingapparatus of claim 32, wherein the notification unit notifies by alarm.35. The portable photographing apparatus of claim 31, wherein thequality evaluation unit causes a focusing to be adjusted on the face inthe received image as detected by the face detection unit.
 36. Theportable photographing apparatus of claim 31, wherein the aspect of thedetection of the face is an illumination condition of the receivedimage.
 37. The portable photographing apparatus of claim 31, wherein theaspect of the detection of the face is a face size of the receivedimage.
 38. The portable photographing apparatus of claim 31, wherein theaspect of the detection of the face is an image blur state of thereceived image.
 39. The portable photographing apparatus of claim 31,further comprising a user interface unit to provide a user interface toallow a user to select an automatic photographing mode or a manualphotographing mode when the face is detected.
 40. A method ofphotographing a picture in a portable photographing apparatus based onface detection, the method comprising: receiving an image; detecting aface from the received image; selectively evaluating a quality of thereceived image based on a certain aspect of the detection of the face,with the quality evaluation being selective based upon a determinationof whether the face is detected in the received image; and notifying auser of a result of the quality evaluation of the received image basedupon the determination of whether the face is detected in the receivedimage.
 41. The method of claim 40, wherein, in the evaluating of thequality of the received image, a focus is adjusted on the face in thereceived image.
 42. The method of claim 40, wherein the aspect of thedetection of the face is an illumination condition of the receivedimage.
 43. The method of claim 40, wherein the aspect of the detectionof the face is a face size of the received image.
 44. The method ofclaim 42, wherein the aspect of the detection of the face is an imageblur state of the received image.
 45. The method of claim 40, whereinthe notifying is by a visual display mechanism.
 46. The method of claim40, wherein the notifying is by alarm.
 47. The method of claim 40,further comprising: providing a user interface to allow a user to selectan automatic photographing mode or a manual photographing mode when theface is detected.
 48. The method of claim 40, wherein, in the selectivequality evaluation, the selective quality evaluation of the receivedimage includes performing the evaluation of the quality of the receivedimage when the determination indicates that the face is detected fromthe received image and not performing the evaluation of the quality ofthe received image when the determination indicates that the face is notdetected from the received image.
 49. The method of claim 48, wherein,in the selective quality evaluation, when the determination indicatesthat the face is not detected from the received image, the receivedimage is not stored and the detecting is performed for a face fromanother received image, subsequent to the received image, and theselective quality evaluation is performed for the other received image,such that the other received image is stored based upon the qualityevaluation of the detected face in the other received image.
 50. Amethod of photographing a picture in a portable photographing apparatusbased on face detection, the method comprising: receiving an image;detecting a face from the received image; evaluating a quality of thereceived image based on a certain aspect of the detection of the face;and notifying a user of the evaluation condition, wherein evaluating ofthe quality of the received image is based at least on a determined facesize of the received image.
 51. A method of photographing a picture in aportable photographing apparatus based on face detection, the methodcomprising: receiving an image; detecting a face from the received imageafter a determination that the face exists in the received image;selectively storing the received image based upon detection of the faceas a face detection moving image or a face detection still image,wherein the selective storing of the received image as the facedetection still image is based upon an evaluation of a quality of thereceived image; and evaluating the quality of the received image, afterthe detection of the face, based on a certain aspect of the detection ofthe face.
 52. The method of claim 51, further comprising notifying auser of the evaluation of the quality of the received image.